<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>请求转发1</title>
<script>
  function inspect() {
    var val = document.frm.param.value;
    return !(val === null || val === "");
  }
</script>
</head>
<body>
  <form name="frm" action="servlet1" method="post">
    <input type="text" name="param" placeholder="参数值">
    <input type="submit" value="提交" onclick="return inspect()">
  </form>
</body>
</html>